Cancer is a major cause of morbidity and mortality in the United States. Treatment of cancer generally includes chemotherapy, radiation therapy and surgery. Unfortunately, most cancers cannot be cured using chemotherapy because tumor cells tend to develop resistance to several chemotherapeutic agents over time. These cancers are referred to as xe2x80x9cmultidrug-resistant cancersxe2x80x9d (MDR).
Overexpression of a number of proteins has been found to be associated with MDR cells lines, including P-glycoprotein (Pgp) and multidrug resistance-associated protein (MRP). These proteins appear to mediate drug resistance by acting as cytotoxic drug efflux pumps. However, many MDR cancer cell lines are known which are not associated with overexpression of either P-glycoprotein or multidrug resistance-associated protein.
More recently, a protein has been described that is overexpressed in MDR tumor cell lines which do not overexpress either P-glycoprotein or multidrug resistance- associated protein. This protein was originally named Lung Resistance-related Protein (LRP), referring to the cell line in which it was originally identified. However, once the cDNA for Lung Resistance-related Protein was isolated and the corresponding protein sequence elucidated, it was found that Lung Resistance-related Protein was human major vault protein, a previously known protein.
Vaults are large, barrel-shaped, multi-subunit, cytoplasmic, ribonucleoprotein organelles found in virtually all higher organisms and in most normal tissues. Mammalian vaults consist of three proteins having molecular weights of approximately 210, 193 and 104, and a small RNA in the relative molar ratios of 1:1:24:4 in rats. The most abundant of these, the 104 kDa protein, is termed major vault protein (MVP) and corresponds to the Lung Resistance-related Protein. The minor vault protein p193, however, has not yet been characterized.
Therefore, there remains a need for chemotherapeutic agents that will target multidrug-resistant cancers. Further, there remains a need to characterize the minor vault protein p193.
According to one embodiment of the present invention, there is provided apolynucleotide molecule encoding human minor vault protein p193, or its complementary strands, and a polynucleotide molecule which hybridizes to such a polynucleotide sequence. According to another embodiment of the present invention, there is provided a vector containing such a polynucleotide and a prokaryotic or eukaryotic host cell stably transformed or transfected by the vector.
According to yet another embodiment of the present invention, there is provided a polynucleotide molecule according to SEQ ID NO: 1, or its complementary strands, and a polynucleotide molecule which hybridizes to such a polynucleotide sequence. According to another embodiment of the present invention, there is provided a vector containing such a polynucleotide and a prokaryotic or eukaryotic host cell stably transformed or transfected by the vector.
According to still another embodiment of the present invention, there is provided a purified and isolated polynucleotide molecule consisting essentially of a nucleotide sequence encoding human minor vault protein p193, or its complementary strands, or a combination of a nucleotide sequence encoding human minor vault protein p193 and its complementary strands, as well as a polynucleotide molecule which hybridizes to such a polynucleotide sequence. According to another embodiment of the present invention, there is provided a vector containing such a polynucleotide and a prokaryotic or eukaryotic host cell stably transformed or transfected by the vector.
Additionally, there is provided a method of making human minor vault protein p193, comprising culturing a microorganism transformed with a polynucleotide according to the present invention; and recovering the human minor vault protein pl93.
These and other features, aspects and advantages of the present invention will become better understood with regard to the following description, appended claims, and accompanying figures where:
FIGS. 1a-1i show the complete sequence of cDNA encoding human minor vault protein 193 and its complementary strand, where the top strand is SEQ ID NO: 1; and
FIG. 2 shows the complete amino acid sequence of human minor vault protein p193 (SEQ ID NO: 2) indicating specific regions of function.